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Period 7.
•Born in Abdera, Elea,
or Miletus in the 5th
Century B.C.
• Lived from 460-370 B.C
• Ancient Greek
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• His mentor was
• The two of them worked
together on atoms
•He was more of a
scientists than other Greek
•Leucippus and Democritus realized that the
world consisted of myriads of indivisible
particles, called atoms which were the smallest
particles of matter possible
•Upon further speculation, they came up with
the idea that the observable properties of
common materials are because of the different
shapes of atoms which they contain, or
different motions of atoms
• Lived from 384 to 322
• He was a Greek
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• A student of Plato and a
teacher of Alexander the
• Had ideas referring to
many different subjects
• Aristotle’s Theory of the Elements: A piece of matter could
be divided an infinite number of times and one would never
find a piece of matter that could be further divided
• He believed in the four elements: earth, fire, water, and air
• According to him, everything in the world was made up of
some combination of these four elements
•At this time this was the most popular theory.
•The atomic theories that were created
at this time were not 100% accurate;
however, they provided insight in an
area never explored before
•The central ideas of Leucippus and
Democritus have remained unchanged
Antoine Lavoisier & The
Law of Conservation of
Born: August 26, 1743
Died: May 8, 1794
“Father of Modern Chemistry”
By: Jin Shin & Taylor Seeman
Educational Background
Attended the College Mazarin at the
request of his aunt
College Mazarin had an excellent
mathematics and science program
Lavoisier was a brilliant student, and
earned numerous awards
He conducted his first few experiments
individually or while aiding professors.
Lavoisier burnt
phosphorous and
sulfur in air and
proved the products
weighed more than the
reactants but the
weight gained was lost
from the air.
When you heat a piece of copper metal in air, it
comes together with oxygen in the air. If you weigh it,
it is found to have a greater mass that the original
piece. However, the mass of the oxygen of the air is
combined with the mass of copper, the mass of the
product is equal to the sum of the masses of the
copper and oxygen that were combined.
Significance of Concept
Showed that the quantity of matter is the
same in the beginning and end of every
chemical reaction, though matter may
change its state.
Though matter may change form, it can
neither be created nor destroyed
Mass of reactants always equal the mass
of products
Significance of Concept
 Law
understanding of
the properties of
movement and
 It is a
principle of
 Sources:
 http://www.biographybas
Joseph Proust: Law of
Definite Proportions
By: Simir and Katie
-born in France (1754-1826)
-son of a pharmacist
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-chief apothecary at Saltpetriere Hospital
-became the director of Royal
Laboratory under Charles IV
-laboratory was destroyed by the
invasion of Spanish Army by Napoleon
so he returned to France
Joseph Proust
-Lived in poverty before being awarded
pension by Louis XVIII
-He taught at the Chemistry school at
Segovia and the University of
Salamanca at Spain
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-He was the chair of this school and was
proposed in 1784 to to train artillery
cadets with the latest scientific
-He worked with Antoine Lavosier
-He also taught chemistry at Musee, a
private school in Paris,
 Proust prepared a copper carbonate
 He heated it, getting rid of the water
and then the carbonic acid, or what was
left of the copper oxide
 - From the 180 lbs of "copper
carbonate" (it was actually carbon
dioxide) he took away 10 lbs of water
and 46 of the carbon dioxide
 - The copper oxide left had 100 lbs of
copper and 25 of oxygen
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Decomposition of CuCO3 into
Cu, C and O
Proust found that the ratio of
the masses of Cu to C to O
was always the same no
matter what size sample of
CuCO3 he started with.
He formed his theory by
dividing to find the ratios
Example Set of Data
Law of Definite Proportions
Copper carbonate must always be made
from the same fixed proportions of copper,
carbon, and oxygen
All compounds contain elements in certain
definite proportions
Ex) Nitric Oxide- 8:7 oxygen to nitrogen
Ex2) Water- 8:1 oxygen to hydrogen
Significance in the
Scientific Community
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 Initially not accepted by all chemists
ie) Claude-Louis Berthollet
argued that elements could combine
in many different proportions (actually
thinking of solutions/mixtures- Proust
was thinking of compounds)
 Law of Definite Proportions was the
basis for John Dalton’s atomic theory
and multiple proportions
Significance in Scientific
Community cont
Proust expanded upon Lavoisier’s Law
of Conservation of Mass
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Law of Conservation of Mass-mass of
reactants was always equal to mass of
products (matter cannot be created or
 Proust measured each individual
substance instead of the total mass for
reactants and products
John Dalton
Early Life
 From Cumberland,
 Birth date is
 Family were
 Worked in the fields
and in the family
cloth shop
 Relatively poor
 Did not get formal
 Did get basic
lessons in reading,
writing, and
John Dalton
Adult Life
 Dalton and his
brother ran a school
in Kendal
 Dalton recorded the
weather patterns
each day (for his
entire life) in a
 Originally wanted to
be a physician,
decided on scientist
 Tutored students at
Dalton’s Law of Multiple
If 2 elements form
multiple compounds,
the ratios of the
masses of the second
element combining
with a fixed mass of
the first element will
be in ratios of small
whole numbers
Dalton’s Law of Multiple
For Example
Elements Y and Z
The weight of Element Z,
when combined with the
fixed weight of element Y,
will compute to a ratio of
small integral numbers
(2:1, 3:1, etc.)
Carbon + Oxygen = CO,
CO2, but not CO1.3
Importance of Dalton’s
Law of Multiple
 One of the
laws of
 Basis for other
Atomic Theories
 Law of
Conservation of
 Law of Definite
Dalton’s Modern Atomic
 All matter is made
of atoms
 Atoms are invisible
and indestructible
 All atoms of a given
element are
identical in mass
and properties
 Compounds are
formed by a
combinations of two
or more different
kinds of atoms
 A chemical reaction
is a rearrangement
of atoms
The Discovery
 Dalton studied gases
 Discovered the partial
pressures of gases
 Lead to formulation of
working theory of the atom
 *Noticed that certain gases
maintained the same ratios of
mixture regardless of amount
 Realized that Ratios remain
the same because they were
consistent down to the
smallest particle or atom
Significance of Dalton’s
Atomic Theory
 First understanding
of the atom
 Prior to, it was an
 The essence of
Dalton’s theory
remains valid
 Led to great
expansion of
theoretical thought
in chemistry
JJ Thomson
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-Discovered the electron and also invented the mass spectrometer
-Interested in sciences as a child and later on his life showed a large interest in
atomic structure
-Graduated and taught at Trinity College after a brief stay at Owens College
-Was an author of many non-fiction science books
Personal Life
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-Born in Cheetham Hill, Manchester on Decemeber 18,
-Full name Sir Joseph John Thomson
-Father died when he was only 16
-In 1890 he married Rose Elizabeth
-He had one son named Sir George Paget Thomson
The Discovery
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-A century ago discovered the electron while using a Cathode
Ray Tube
-Cathode Ray Tube is a glass tube that has wiring attached to its
two sides.
-The air is taken out and in order to try and form a vacuum.
-An electric charge goes from one end to the other and produces
a glow that looks fluorescent.
-A cathode ray or electron gun is attached to the glass
The Experiment
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-Used his Cathode Ray Tube made a unique tube to probe
that the rays shot in had a negative charge.
-Almost perfect vacuum and he put the fluorescent layer
on a specific side.
- Had an electric plate, this gave a positive charged
electrode to the negative cathode. The ray would be
-Shot a ray got deflected by the opposite positive charge.
This showed that the ray was made up of charged,
The Third Experiment
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-Figured out that the charge to mass ratio could have been
very large or extremely small
-Chose correctly that they were very small
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-Later Devices, helps with electronic devices, making
impulses so a screen can run and one can see a display.
-Cathode-Ray Tube can produce an image on a screen with
electrical impulses.
-It can primarily help with TV screens and computer
Robert Andrews Millikan
-born in 1868 in Illinois
-grew up in Iowa
-worked on Oil Drop Experiment in University of
Chicago (professor)
-1923: Nobel Prize for Physics
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The Discovery
 At University of Chicago
 Performed a series of
 Wanted to find the
charge of an election
 Worked off Thomson’s
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The Experiment
The atomizer produces fine oil droplets
Oil droplets fall through a hole in the first
chamber as a stream of tiny droplets
X-rays negatively charge the oil droplets
An applied voltage on two plates surrounding
the oil drops creates an electric field. The
electric force pull some drop upward.
The rate at which the oil droplets are falling
and rising between the two charged plates is
measured through the microscope.
The Experiment
 Some oil droplets fell, and some did not
 This depended on the forces acting upon it: electric force,
gravitational force, and air resistance
 He found…
 1. When a large electric field is applied, but the electric force
on the droplet is larger, then the gravitation force acts in the
opposite direction: it moves upward
 2. Net force of a droplet=sum of the gravitational force, the air
resistance, and electrical force
 V1=k(Eq-mq)
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The Experiment
 In simpler terms…
 When there was no voltage applied, the droplet
would fall down to the bottom
 Voltage applied, droplets with negative charge
drop more slowly, stop altogether, or even go up
(depending on the voltage given)
 Charges of the droplets were all multiples of the
smallest value
 e-=1.6 x 10 to the -19 coulombs
Significance of Experiment
Calculated charge
of electron
Showed that
charge on electron
was smallest
possible amount of
Total amount of
electric charge
must always be an
integer multiple of
this electric charge
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Significance of
Now that the charge of an electron is
discovered, further advancements in
science can be made on the atom
An atom is the basic unit of an element
With the discovery of an electron, we
can find out more on the states of
substances, elements, etc.
Without him, chemistry would not have
advanced much
Earnest Rutherford
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As well as Marsden and Geiger
and their gold foil experiment
Background Info
 Ernest Rutherford, 1st Baron Rutherford of
Nelson was a British-New Zealand chemist and
physicist. In his early work he discovered the
concept of radioactive half and also differentiated
and named alpha and beta radiation. He was
awarded the Nobel Prize in Chemistry in 1908 "for
his investigations into the disintegration of the
elements, and the chemistry of radioactive
Before his Experiment
Before his experiment people though that the
particles in an atom were randomly arranged
according to the plum pudding model. See
diagram below.
Rutherford thought that if the plum pudding
model was correct then a beam of alpha
particles would go though matter with very
little deflection. See diagram below.
Rutherford’s experiment consisted of a block of
radium to generate alpha particles, gold foil for
the particles to pass trough and a florescent
screen that he could use to determine where the
alpha particles ended up. See diagram below.
The Gold Foil experiment showed that the plum pudding model of
the atom was not accurate. This is because the experiment
showed how there had to be a piece of the atom with a large
mass in the center of the atom. The realization that things were
not just loosely "hanging out" around an atom but instead are
arranged in a specific way around a center led him to discover the
Atomic Nucleus. See diagram below
More Conclusions
Without this discovery, much of what we know about atoms would
not be possible. If not for the discovery of the nucleus, we could
not know about the important parts that it consists of (protons
and neutrons). Also, the periodic table of elements that we all
know so well (from intense memorization for Chemistry tests),
the elements would not be ordered the same way, because
Atomic number is the number of protons in the nucleus of an
atom. Also, we can also identify different atoms by mass number.
This is the number of protons and neutrons added together in the
nucleus. All these things, and many more, that are the basis of
our knowledge of atoms would not be possible without the
information from Rutherford's Gold Foil Experiment.
James Chadwick Background
•Chadwick was born in Cheshire,
England in 1891.
•He went to Manchester University in
•After college, he spent his time studying
under Professor Rutherford.
•Professor Rutherford created the first
artificial nuclear transformation.
•This is where he made studies on
atomic nuclei.
•In 1921, he became Assistant Director
of Research of the Cavendish
•In 1927, he was elected a Fellow of the
Royal Society.
Background Info (con’t)
In 1932, he discovered the
existence of neutrons.
For this he was awarded the
Hughes Medal of the royal
He was later awarded the Nobel
Peace Prize in 1935 for physics.
From 1943 to 1946, he worked
in the United States on the
Manhattan Project for the
development of the atomic
He retired in England in 1948.
He died in 1974.
Neutron Discovery
Rutherford discovered the proton in the nucleus
Noticed it was not the only particle in the nucleus
Atomic mass could not only be the mass of protons (e.g. Helium
has an atomic mass of 4, but the number of protons is 2
Chadwick went further in trying to discover the neutron, and kept on trying,
even as he failed.
Walter Bothe and Herbert Becker did experiments with beryllium where it
emitted radiation to penetrate 200 mLs of lead. They thought this was high
energy gamma rays, but Chadwick noticed it was something else
Without the clues and inspirations of Rutherford, Bothe, and
Becker, Chadwick would not have been able to discover the
Neutron Discovery (Cont.)
Two other scientists, Federic and Irlene Joliot-Curry, tracked particle radiation
by putting paraffin wax in front of the rays (thought to be gamma rays) coming
from the beryllium. During this, they observed high-speed protons coming out
the paraffin.
Chadwick recognized the rays from the beryllium were not
gamma rays because they were too strong. He concluded that
they were neutrons. He did his own experiments to back this up.
Since neutrons are neutral, they can penetrate thick layers of
different substances because they are not disturbed by positive
or negative charges.
Chadwick also discovered that the mass of a neutron is 1.0067
The Neutron Experiment
By knowing about the
neutron, scientists
could use atomic
number and atomic
mass because they
were no longer
extremely similar.
Also, knowing about
neutrons was important
in the creation of
nuclear weapons and
nuclear reactors.
In addition, the
creation of plutonium235 and uranium-235
is caused by their
absorption of neutrons.
Significance (Cont.)
At extremely high pressure and temperature, neutrons and electrons
collapse into neutronic matter, known as neutronium.
This is what happens in neutron stars
Neutron capture results in neutron activation, which creates
Used to excited delayed and prompy gamma rays from elements in
Neutron emitters can detect light in the nuclei, especially hydrogen
found in water molecules.
Niels Bohr
Born: Copenhagen,
Denmark, in 1885
Died: Copenhagen,
Denmark, in 1962 of
heart failure
A Doctor of Physics
Background Info.
Awarded Nobel Prize for his work in
the structure of atoms in 1922
Worked under J.J. Thomson in
Cambridge, and later with Ernest
Rutherford in Manchester University,
in the field of physics
The Bohr Model
Developed model of
atom in which
electrons orbited the
nucleus in certain
energy levels. Called
the Bohr Model.
Conducted the Liquid
Drop Experiment.
The Shell Model
Developed Shell Model in which
the outermost orbit of electrons
determined the chemical
properties of the element.
Significance of Bohr and
Shell Model
 Shell Model is used as a basis for Chemistry,
since Chemistry is about the RXNS and
interactions between elements/chemicals
 The Bohr Model gave a more accurate model
of an atom. The fact that electron movement
was not applicable in classical mechanics
caused the introduction of quantum mechanics
into modern science.
Contributions, cont.
 Helped develop the Atomic Bomb
(part of Manhattan
Project/Atomic Energy Project)
 Began work in Theoretical
Quantum Physics (Old Quantum
 Identified isotope of Uranium
responsible for slow-neutron
Works Cited Proust
Ricki Harris and Jodi Lefkowitz
Thomson sources
Work cited
Wikipedia contributors. "Ernest Rutherford." Wikipedia, The
Free Encyclopedia. Wikipedia, The Free Encyclopedia, 11
Sep. 2010. Web. 22 Sep. 2010.
"Ernest Rutherford - Biography". 21 Sep